Pressure accumulators are widely used in many types of hydraulic systems. One type of pressure accumulator comprises a thimble-shaped flexible bladder mounted in a rigid shell, the bladder serving to separate the interior of the shell into two separate compartments which are sealed from one another. A first valved port is provided at one end of the shell in communication with one of the compartments which is termed the "liquid compartment", and a second valved port is provided at the other end of the shell, termed the "valved gas precharge port", is communication with the other compartment which is termed the "gas precharge compartment".
A compressible gas, such as nitrogen, is permanently charged and compressed under high pressure and introduced through the gas precharge port into the gas compartment of the accumulator. Then, an incompressible hydraulic liquid under high pressure is pumped through the valved liquid port into the liquid compartment. The flexible bladder is gradually forced into the gas compartment as the liquid is pumped into the liquid compartment, thereby compressing the gas in the gas compartment until a balanced higher pressure is reached in both compartments. In this way, energy is stored or absorbed into the gas compartment of the accumulator, and this energy acts as a spring to force the imcompressible hydraulic liquid out through the liquid port, thereby causing the hydraulic liquid to do useful work.
It is the usual practice to provide a spring-loaded poppet in the liquid port of the accumulator to prevent the bladder from extruding out through the liquid port. Under normal conditions this poppet valve is held open by a spring, and it is closed by the action of the bladder engaging the poppet after all of the liquid has been expelled from the liquid compartment thus preventing the gas precharge pressure from forcing the bladder out through the liquid port.
In the accumulator of the present invention, the gas precharge compartment is adjacent the cap at the open end of the shell, and the valved gas precharge port is mounted in the cap. A thimble-shaped flexible bladder is provided in the shell, and the mouth of the bladder is sealed to the cap, as will be described. This bladder separates the gas precharge compartment from the liquid compartment.
As mentioned above, the spring-loaded poppet valve in the liquid port at the other end of the shell has a unique construction, in that it is impossible to disassemble the valve so long as a precharge exists in the gas precharge compartment within the shell. This constitutes an important safety factor.